To realize its full potential for biology and medicine, genomics requires classification of vertebrate genes and other genomic features, e.g., as "shared with vertebrates" or "shared with animals." Such classification is the first step towards a general understanding of the content of genomes. Research on "worms and flies," the best-studied invertebrate model systems of modern biology, provides the beginnings of such a classification for the vertebrates. Most recent animal phylogenies, however, suggest that nematodes (worms) and arthropods (flies) not only may be relatively derived animals but may also share some derived characteristics. Worms and flies may thus have had a complex evolutionary history together, a history not shared by vertebrate lineages. Without knowledge of simple, primitive animals, it is impossible to effectively classify the content of vertebrate genomes. Recent phylogenies generally agree that the simplest, most primitive animals are represented by four groups: sponges, placozoans, cnidarians, and ctenophores. Here we focus on three of these basal metazoan groups: (1) ctenophores, which are often considered to be the sister group of the bilaterians, (2) cnidarians, which include some of the best-studied basal metazoans, and (3) placozoans, which exhibit a number of unique and enigmatic characteristics including the smallest genome yet found in a metazoan. With the recent initiation of genomic projects using cnidarians (e.g. the hydroid EST project and the Nematostella BAC library project), it is timely to consider basal metazoans in the broader context of genomics. We propose a Society for Integrative and Comparative Biology (SICB) symposium, scheduled for January 5-6, 2004, in New Orleans, "Model systems for the basal metazoans: cnidarians, ctenophores, and placozoans." The goals of the symposium will be to bring together a diverse group of molecular, cellular, organismal, and evolutionary biologists to discuss appropriate basal metazoan models that can provide a comparative context for vertebrate models. Ultimately, this work will allow the power of genomics to be fully realized in biology and medicine. [unreadable] [unreadable]